# Copyright (c) 2015, Frappe Technologies Pvt. Ltd. and Contributors
# License: GNU General Public License v3. See license.txt

from __future__ import unicode_literals
import frappe
from frappe import _
from frappe.utils import cstr, flt
import json, copy

from six import string_types

class ItemVariantExistsError(frappe.ValidationError): pass
class InvalidItemAttributeValueError(frappe.ValidationError): pass
class ItemTemplateCannotHaveStock(frappe.ValidationError): pass

@frappe.whitelist()
def get_variant(template, args=None, variant=None, manufacturer=None,
	manufacturer_part_no=None):
	"""Validates Attributes and their Values, then looks for an exactly
		matching Item Variant

		:param item: Template Item
		:param args: A dictionary with "Attribute" as key and "Attribute Value" as value
	"""
	item_template = frappe.get_doc('Item', template)

	if item_template.variant_based_on=='Manufacturer' and manufacturer:
		return make_variant_based_on_manufacturer(item_template, manufacturer,
			manufacturer_part_no)
	else:
		if isinstance(args, string_types):
			args = json.loads(args)

		if not args:
			frappe.throw(_("Please specify at least one attribute in the Attributes table"))
		return find_variant(template, args, variant)

def make_variant_based_on_manufacturer(template, manufacturer, manufacturer_part_no):
	'''Make and return a new variant based on manufacturer and
		manufacturer part no'''
	from frappe.model.naming import append_number_if_name_exists

	variant = frappe.new_doc('Item')

	copy_attributes_to_variant(template, variant)

	variant.manufacturer = manufacturer
	variant.manufacturer_part_no = manufacturer_part_no

	variant.item_code = append_number_if_name_exists('Item', template.name)

	return variant

def validate_item_variant_attributes(item, args=None):
	if isinstance(item, string_types):
		item = frappe.get_doc('Item', item)

	if not args:
		args = {d.attribute.lower():d.attribute_value for d in item.attributes}

	attribute_values, numeric_values = get_attribute_values(item)

	for attribute, value in args.items():
		if not value:
			continue

		if attribute.lower() in numeric_values:
			numeric_attribute = numeric_values[attribute.lower()]
			validate_is_incremental(numeric_attribute, attribute, value, item.name)

		else:
			attributes_list = attribute_values.get(attribute.lower(), [])
			validate_item_attribute_value(attributes_list, attribute, value, item.name)

def validate_is_incremental(numeric_attribute, attribute, value, item):
	from_range = numeric_attribute.from_range
	to_range = numeric_attribute.to_range
	increment = numeric_attribute.increment

	if increment == 0:
		# defensive validation to prevent ZeroDivisionError
		frappe.throw(_("Increment for Attribute {0} cannot be 0").format(attribute))

	is_in_range = from_range <= flt(value) <= to_range
	precision = max(len(cstr(v).split(".")[-1].rstrip("0")) for v in (value, increment))
	#avoid precision error by rounding the remainder
	remainder = flt((flt(value) - from_range) % increment, precision)

	is_incremental = remainder==0 or remainder==increment

	if not (is_in_range and is_incremental):
		frappe.throw(_("Value for Attribute {0} must be within the range of {1} to {2} in the increments of {3} for Item {4}")\
			.format(attribute, from_range, to_range, increment, item),
			InvalidItemAttributeValueError, title=_('Invalid Attribute'))

def validate_item_attribute_value(attributes_list, attribute, attribute_value, item):
	allow_rename_attribute_value = frappe.db.get_single_value('Item Variant Settings', 'allow_rename_attribute_value')
	if allow_rename_attribute_value:
		pass
	elif attribute_value not in attributes_list:
		frappe.throw(_("Value {0} for Attribute {1} does not exist in the list of valid Item Attribute Values for Item {2}").format(
			attribute_value, attribute, item), InvalidItemAttributeValueError, title=_('Invalid Attribute'))

def get_attribute_values(item):
	if not frappe.flags.attribute_values:
		attribute_values = {}
		numeric_values = {}
		for t in frappe.get_all("Item Attribute Value", fields=["parent", "attribute_value"]):
			attribute_values.setdefault(t.parent.lower(), []).append(t.attribute_value)

		for t in frappe.get_all('Item Variant Attribute',
			fields=["attribute", "from_range", "to_range", "increment"],
			filters={'numeric_values': 1, 'parent': item.variant_of}):
			numeric_values[t.attribute.lower()] = t

		frappe.flags.attribute_values = attribute_values
		frappe.flags.numeric_values = numeric_values

	return frappe.flags.attribute_values, frappe.flags.numeric_values

def find_variant(template, args, variant_item_code=None):
	conditions = ["""(iv_attribute.attribute="{0}" and iv_attribute.attribute_value="{1}")"""\
		.format(frappe.db.escape(key), frappe.db.escape(cstr(value))) for key, value in args.items()]

	conditions = " or ".join(conditions)

	# use approximate match and shortlist possible variant matches
	# it is approximate because we are matching using OR condition
	# and it need not be exact match at this stage
	# this uses a simpler query instead of using multiple exists conditions
	possible_variants = frappe.db.sql_list("""select name from `tabItem` item
		where variant_of=%s and exists (
			select name from `tabItem Variant Attribute` iv_attribute
				where iv_attribute.parent=item.name
				and ({conditions}) and parent != %s
		)""".format(conditions=conditions), (template, cstr(variant_item_code)))

	for variant in possible_variants:
		variant = frappe.get_doc("Item", variant)

		if len(args.keys()) == len(variant.get("attributes")):
			# has the same number of attributes and values
			# assuming no duplication as per the validation in Item
			match_count = 0

			for attribute, value in args.items():
				for row in variant.attributes:
					if row.attribute==attribute and row.attribute_value== cstr(value):
						# this row matches
						match_count += 1
						break

			if match_count == len(args.keys()):
				return variant.name

@frappe.whitelist()
def create_variant(item, args):
	if isinstance(args, string_types):
		args = json.loads(args)

	template = frappe.get_doc("Item", item)
	variant = frappe.new_doc("Item")
	variant.variant_based_on = 'Item Attribute'
	variant_attributes = []

	for d in template.attributes:
		variant_attributes.append({
			"attribute": d.attribute,
			"attribute_value": args.get(d.attribute)
		})

	variant.set("attributes", variant_attributes)
	copy_attributes_to_variant(template, variant)
	make_variant_item_code(template.item_code, template.item_name, variant)

	return variant

@frappe.whitelist()
def enqueue_multiple_variant_creation(item, args):
	# There can be innumerable attribute combinations, enqueue
	if isinstance(args, string_types):
		variants = json.loads(args)
	total_variants = 1
	for key in variants:
		total_variants *= len(variants[key])
	if total_variants >= 600:
		frappe.msgprint("Please do not create more than 500 items at a time", raise_exception=1)
		return
	if total_variants < 10:
		return create_multiple_variants(item, args)
	else:
		frappe.enqueue("erpnext.controllers.item_variant.create_multiple_variants",
			item=item, args=args, now=frappe.flags.in_test);
		return 'queued'

def create_multiple_variants(item, args):
	count = 0
	if isinstance(args, string_types):
		args = json.loads(args)

	args_set = generate_keyed_value_combinations(args)

	for attribute_values in args_set:
		if not get_variant(item, args=attribute_values):
			variant = create_variant(item, attribute_values)
			variant.save()
			count +=1

	return count

def generate_keyed_value_combinations(args):
	"""
	From this:

		args = {"attr1": ["a", "b", "c"], "attr2": ["1", "2"], "attr3": ["A"]}

	To this:

		[
			{u'attr1': u'a', u'attr2': u'1', u'attr3': u'A'},
			{u'attr1': u'b', u'attr2': u'1', u'attr3': u'A'},
			{u'attr1': u'c', u'attr2': u'1', u'attr3': u'A'},
			{u'attr1': u'a', u'attr2': u'2', u'attr3': u'A'},
			{u'attr1': u'b', u'attr2': u'2', u'attr3': u'A'},
			{u'attr1': u'c', u'attr2': u'2', u'attr3': u'A'}
		]

	"""
	# Return empty list if empty
	if not args:
		return []

	# Turn `args` into a list of lists of key-value tuples:
	# [
	# 	[(u'attr2', u'1'), (u'attr2', u'2')],
	# 	[(u'attr3', u'A')],
	# 	[(u'attr1', u'a'), (u'attr1', u'b'), (u'attr1', u'c')]
	# ]
	key_value_lists = [[(key, val) for val in args[key]] for key in args.keys()]

	# Store the first, but as objects
	# [{u'attr2': u'1'}, {u'attr2': u'2'}]
	results = key_value_lists.pop(0)
	results = [{d[0]: d[1]} for d in results]

	# Iterate the remaining
	# Take the next list to fuse with existing results
	for l in key_value_lists:
		new_results = []
		for res in results:
			for key_val in l:
				# create a new clone of object in result
				obj = copy.deepcopy(res)
				# to be used with every incoming new value
				obj[key_val[0]] = key_val[1]
				# and pushed into new_results
				new_results.append(obj)
		results = new_results

	return results

def copy_attributes_to_variant(item, variant):
	# copy non no-copy fields

	exclude_fields = ["naming_series", "item_code", "item_name", "show_in_website",
		"show_variant_in_website", "opening_stock", "variant_of", "valuation_rate"]

	if item.variant_based_on=='Manufacturer':
		# don't copy manufacturer values if based on part no
		exclude_fields += ['manufacturer', 'manufacturer_part_no']

	allow_fields = [d.field_name for d in frappe.get_all("Variant Field", fields = ['field_name'])]
	if "variant_based_on" not in allow_fields:
		allow_fields.append("variant_based_on")
	for field in item.meta.fields:
		# "Table" is part of `no_value_field` but we shouldn't ignore tables
		if (field.reqd or field.fieldname in allow_fields) and field.fieldname not in exclude_fields:
			if variant.get(field.fieldname) != item.get(field.fieldname):
				if field.fieldtype == "Table":
					variant.set(field.fieldname, [])
					for d in item.get(field.fieldname):
						row = copy.deepcopy(d)
						if row.get("name"):
							row.name = None
						variant.append(field.fieldname, row)
				else:
					variant.set(field.fieldname, item.get(field.fieldname))

	variant.variant_of = item.name

	if 'description' not in allow_fields:
		if not variant.description:
				variant.description = ""

		if item.variant_based_on=='Item Attribute':
			if variant.attributes:
				attributes_description = item.description + " "
				for d in variant.attributes:
					attributes_description += "<div>" + d.attribute + ": " + cstr(d.attribute_value) + "</div>"

				if attributes_description not in variant.description:
					variant.description += attributes_description

def make_variant_item_code(template_item_code, template_item_name, variant):
	"""Uses template's item code and abbreviations to make variant's item code"""
	if variant.item_code:
		return

	abbreviations = []
	for attr in variant.attributes:
		item_attribute = frappe.db.sql("""select i.numeric_values, v.abbr
			from `tabItem Attribute` i left join `tabItem Attribute Value` v
				on (i.name=v.parent)
			where i.name=%(attribute)s and (v.attribute_value=%(attribute_value)s or i.numeric_values = 1)""", {
				"attribute": attr.attribute,
				"attribute_value": attr.attribute_value
			}, as_dict=True)

		if not item_attribute:
			return
			# frappe.throw(_('Invalid attribute {0} {1}').format(frappe.bold(attr.attribute),
			# 	frappe.bold(attr.attribute_value)), title=_('Invalid Attribute'),
			# 	exc=InvalidItemAttributeValueError)

		abbr_or_value = cstr(attr.attribute_value) if item_attribute[0].numeric_values else item_attribute[0].abbr
		abbreviations.append(abbr_or_value)

	if abbreviations:
		variant.item_code = "{0}-{1}".format(template_item_code, "-".join(abbreviations))
		variant.item_name = "{0}-{1}".format(template_item_name, "-".join(abbreviations))

@frappe.whitelist()
def create_variant_doc_for_quick_entry(template, args):
	variant_based_on = frappe.db.get_value("Item", template, "variant_based_on")
	args = json.loads(args)
	if variant_based_on == "Manufacturer":
		variant = get_variant(template, **args)
	else:
		existing_variant = get_variant(template, args)
		if existing_variant:
			return existing_variant
		else:
			variant = create_variant(template, args=args)
			variant.name = variant.item_code
			validate_item_variant_attributes(variant, args)
	return variant.as_dict()

